There are various applications in which the operation of equipment may advantageously be limited to a certain predefined geographic area. One example of such an application is in the field of communications. The number of potential users for any given portion of the communication spectrum is much greater than the available bandwidth in most areas. One method for accommodating the various potential users is to prioritize the uses of the frequency band. Prioritization allows a low priority user to access the band when the high priority users are not using the band, thereby allowing the band to be used without interfering with the high priority usage. To prevent lower priority systems from causing interference to higher priority systems, it may be necessary to forbid the operation of the lower priority systems in certain geographical areas.
For example, under the current Federal Communications Commission (FCC) rules, wireless equipment operating in the Unlicensed Personal Communications Services (U-PCS) allocation 1910-1930 MHz will only be allowed in areas in which the equipment will not interfere with the microwave links currently operating in that spectral allocation. If the equipment is moved into a region in which it might cause interference to such microwave links, it must shut down.
Equipment that is capable of such controllable behavior is referred to as "coordinatible." Similarly, equipment that is not capable of such behavior is said to be "non-coordinatible." A wireless PBX (W-PBX) is an example of a coordinatible system. The handset is designed to shut down outside of range of the W-PBX, and the W-PBX can be made difficult to transport into a region in which it could cause interference. In contrast, a residential cordless phone is noncoordinatible. While the handset is also designed to shut down outside of range of its base station, the base station and handset can easily be moved together to another location in which the system may cause interference.
Under the plan and program mandated by the FCC, an agency will be empowered to arrange and schedule the shutting down of existing microwave links operating in the U-PCS allocation, on a regional basis. As each region is cleared out, coordinatible equipment can be deployed in the U-PCS spectrum in that region; whereas non-coordinatible equipment cannot be deployed there. Once all of the equipment is replaced by coordinatible equipment, the interference problems will be substantially reduced.
At present, no completely adequate method for implementing the coordination scheme has been approved. While the coordination of the handsets of wireless phones is relatively simple to implement if the base stations are fixed, coordination of base station operation is more difficult. The handset can be programmed to shut down if it does not receive a signal from its base station. However, one must still provide some method for shutting down the base station if it is moved from its approved geographic area.
It has been suggested that the coordination of the base station and/or handset can be accomplished by requiring the coordinatible equipment to shut down if it is not within range of a high powered transmitter such as an FM broadcasting station. However, this proposal requires the equipment to be set up based on the pattern and power levels of existing FM broadcasting stations in each region. This pattern changes with time. In addition, the pattern of stations in any geographic area is not necessarily unique. Furthermore, counterfeit FM signals can be generated that would allow a coordinatible system to run outside its area of intended use. Finally, there are areas of the country in which suitable FM broadcast stations are not available.
It is one object of the present invention to provide an improved method for enforcing geographic restrictions on coordinatible radio equipment.
It is a further object of the present invention to provide a system for restricting the operation of coordinatible radio equipment even if the equipment is moved to a new location.
It is a still further object of the present invention to provide a coordinatible equipment system that provides protection against accidental or intentional enablement in an unauthorized area because of the presence of a broadcast source in the unauthorized area.
These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description of the invention and the accompanying drawings.